The physical compression running through the couplers and draft gear of a train when slack bunches up. This force occurs during braking, descending grades, or when a pusher locomotive shoves from the rear. Managing the balance between buff and draft forces is the core skill of train handling to prevent derailments.
Heard on the job
You need to keep the head end stretched out, if you let too much buff build up on this curve you'll pop a car right off the rail.
Also heard as
- buff force
Do not mix it up with
- Draft: Buff is the force of cars pushing together; draft is the force of cars pulling apart.
Related terms
Slack
The free play in couplers and draft gear that lets cars move a little toward or away from each other.
Draft
The pulling force stretching the couplers and draft gear of a train.
Dynamic braking
Retarding force made by turning a locomotive's traction motors into generators and burning the energy off as heat.